The UVSunSense wristband, whose technology was developed by a nuclear physicist, instantly tells you when your sunscreen is working and when it's not. As you apply sunscreen to your body (please use 1 ounce, or a shot glass full), you also apply it on the band (by the way, this product only works with SPF 15 or higher). The band, which uses photochromatic dyes, immediately turns purple in the sun, indicating that you're protected. The color of the band will turn to a lavender color when your sunscreen is wearing off and it's time to reapply. As you might expect, the higher the SPF, the longer it takes to reach this color. If the band becomes a pale yellow, you're completely exposed and probably should get out of the sun. I think that this product is a great help for getting in the habit of regularly reapplying sunscreen, and can be a safeguard in case you've forgotten to reapply. Furthermore, the product works even in salt or chlorinated water, so it's really versatile and ready for any of your summer activities. This also could be a great and fun way to introduce kids to the idea of sun protection and getting accustomed to regular sunscreen application.